1. Field of the Invention
The present invention relates generally to an apparatus for holding an object in a predetermined position relative to an external metal member, and methods of constructing and utilizing such an appartus.
More particularly, the invention relates to a magnetic holding apparatus for holding in place bricks or blocks used for lining or re-lining furnaces and kilns having metallic shells.
2. Description of Relevant Art
Many furnaces and kilns are conventionally constructed by initially fabricating a shell formed of steel or some other high-strength metal. The metallic shell is then lined and insulated with various refractory materials, such as fire brick, kiln brick or block, or furnace block. For example, construction of various cylindrical or rotary furnaces and kilns begins with a cylindrical steel shell. Arcuate or wedge-shaped refractory blocks or bricks are then lined along the interior of the cylindrical steel shell. A prevalent conventional technique for constructing the brick lining is to use arcuate or wedge-shaped refractory blocks which require no mortar or cement between adjacent blocks. The blocks are retained in place in the lining by the compressive force exerted when the final block is installed.
One example of a kiln or furnace which requires extensive and difficult provisions to hold the refractory brick in place during construction is known as a rotary kiln. A rotary kiln is a long tubular structure, mounted on rollers in a general horizontal orientation, with a slight slope. To contain heat in the interior of the kiln and to provide a renewable wear surface, the inner cylindrical surface of the metallic shell of the rotary kiln is lined with a multiplicity of circumferential rows of rotary kiln blocks. A rotary kiln block has the general configuration of a wedge, with one surface being arcuate to conform to the interior surface of the shell of the kiln.
In general, lining or re-lining of the upper arcuate portion of a rotary kiln or other similarly constructed kiln or furnace is performed as follows.
First, a scaffold is provided so as to afford a working support surface for construction workers within the kiln. The scaffold may be formed by wedging joist members across the interior of the kiln, and then fixing transverse plans to the joists so as to define a floor surface. Alternatively, the scaffold may take the form of a steel scaffold provided with wheels which permit the scaffold to be easily rolled along the interior of the kiln as work progresses. Generally, the scaffold is approximately eight feet in length, and is moved after approximately each six-foot longitudinal section of block-installing work has been completed.
Next, a wooden form or frame having a general semicircular configuration is disposed on the work platform or scaffold such that the arcuate portion thereof generally follows the arcuate inner upper surface of the kiln shell. Such a wooden form is conventionally known as a "center" member, and is employed to support a plurality of block-supporting devices known conventionally as "pogo sticks". The pogo sticks comprise threaded rods received within a steel pipe provided with a collar at one end thereof. A compression spring fits over the threaded rod and is supported by the collar on the steel pipe. A nut is threadedly received on the threaded rod, and by tightening or loosening the nut along the threaded rod, the overall length of the pogo stick may be adjusted. In employing the pogo stick for positioning a block against the inner surface of the kiln shell, the length of the pogo stick is suitably adjusted such that it may be wedged between the exposed lower side of the block and the upper arcuate surface of the center member.
A plethora of problems are associated with the above-described block-supporting technique for lining or re-lining the shell of a kiln. Because approximately 35 to 85 pogo sticks are commonly simultaneously supported by the center member, it is ofttimes extremely difficult to transport blocks from the forward side of the scaffold to the rear side thereof, where the block positioning work normally takes place. Another significant drawback of such conventional technique relates to safety of the workers themselves. For example, in the event that a single brick is inadvertently dropped on the wooden center member, or in the event that a single pogo stick slips out of position such tht the brick it supports drops onto the center member, other adjacent pogo sticks are likely to be struck by the falling brick. In this manner, there is a likelihood of a "chain reaction" effect, whereby more and more of the falling bricks displace more and more of the pogo sticks. Such a situation is extremely hazardous to the workers, not only with regard to the possibility that the workers will be struck by the falling bricks, but also because the scaffold may be stressed to the point of tumbling down. Furthermore, adjusting the pogo sticks to the required lengths and wedging them between the brick and the center member has proven to be a difficult and time-consuming task.
The present invention effectively solves the foregoing problems attendant the conventional technique, and provides an apparatus and method which is very easy and convenient to use, reduces working time, reduces costs, and moreover enhances the safety of the workers themselves.